In recent years, with miniaturization of an internal device of electronic equipment having been advanced for a variety of purposes, miniaturization of each component constituting the internal device, such as a power supply, has also been desired. However, with a mounting board for use in the miniaturized internal device also miniaturized, there has been a problem in that a connection area of each component to be mounted on this mounting board cannot be sufficiently ensured and fixing strength of each component thus cannot be held. Further, since the start of mounting of a coin-type electric double-layered capacitor as such a component in portable electronic equipment, the coin-type electric double-layered capacitor has also been desired to have fixing strength capable of withstanding impact from any direction on the assumption of a variety of equipment usage patterns.
Incidentally, as a fixing method for connecting the coin-type electric double-layered capacitor to the mounting board in consideration of efficient mass-production, reflow-soldering has generally been conducted. However, in the case of mass-producing mounting boards each fixed with the coin-type electric double-layered capacitor by means of this reflow-soldering, it is difficult to unify a condition of fixing of the coin-type electric double-layered capacitor to each mounting board by solder. Therefore, there has thus been a problem in that a mounting board having insufficient fixing strength and insufficiently fixed with the coin-type electric double-layered capacitor may be produced.
Such a problem with the connection of the conventional coin-type electric double-layered capacitor to the mounting board is specifically described with reference to drawings.
FIG. 6A is a top view showing a configuration of a conventional coin-type electric double-layered capacitor, and FIG. 6B is a side view of a configuration of the same coin-type electric double-layered capacitor.
As shown in FIGS. 6A and 6B, the conventional coin-type electric double-layered capacitor is configured such that a capacitor element (not shown) for charging and discharging electricity is arranged inside and surrounded by use of metal-made upper cover 601 and lower cover 602, which is caulked through a ring-shaped packing having insulating properties. Upper cover 601 and lower cover 602 are electrically connected with the capacitor element, thereby to have polarities different from those of upper cover 601 and lower cover 602 respectively, constituting a body section of the coin-type electric double-layered capacitor. Further, upper terminal plate 604 is electrically connected with outer surface 601a of upper cover 601. This upper terminal plate 604 forms a step shape in a longitudinal direction, and is electrically connected in the state of being in contact with the surface of a mounting board (not shown) located below the coin-type electric double-layered capacitor. Further, upper terminal plate 604 is configured to have plated section 604b, having been subjected to plating processing, at its one end portion in the longitudinal direction which is electrically connected with the mounting board. Moreover, notched section 607 is provided on each side surface in a width direction of this plated section 604b. 
Lower terminal plate 603 is electrically connected to outer surface 602a of lower cover 602. Lower terminal plate 603 has a flat plate shape, and is electrically connected in the state of being in contact with the surface of the mounting board located below this lower terminal plate 603. Similarly to upper terminal plate 604, lower terminal plate 603 is also configured to have plated section 603b, having been subjected to plating processing, at its one end portion in the longitudinal direction which is electrically connected with the mounting board. Moreover, similarly to upper terminal plate 604, notched section 608 is provided on each side surface in the width direction of this plated section 603b. 
With such a configuration, in the conventional coin-type electric double-layered capacitor, at the time of independently connecting upper terminal plate 604 and lower terminal plate 603 to the mounting board through solder, surface areas of the side surfaces of plated sections 603b, 604b are extended due to provision of notched sections 607, 608, to increase an area for forming a solder fillet. This can increase areas of the connection portions between plated sections 603b, 604b and the mounting board, so as to enhance fixing strength of the coin-type electric double-layered capacitor to the mounting board.
Namely, in the case of plated sections 603b, 604b not having respective notched sections 607, 608, the connection portions between plated sections 603b, 604b and the mounting board are fixed by solder fillets formed on the side surfaces in the longitudinal direction and both side surfaces in the width direction of plated sections 603b, 604b. As opposed to this, in the case of plated sections 603b, 604b having respective notched sections 607, 608, the solder fillets formed on the side surfaces in the longitudinal direction of plated sections 603b, 604b are also formed on the side surfaces of notched sections 607, 608, and hence the fillets increase. This can efficiently enhance the fixing strength of the connection portions between plated sections 603b, 604b and the mounting board.
It should be noted that as document information related to this prior art, for example, Patent Document 1 is known.
However, as for the coin-type electric double-layered capacitor, further miniaturization has been desired, and there has been a problem of difficulty in ensuring fixing strength at the time of connecting a further miniaturized coin-type electric double-layered capacitor to the mounting board. Namely, there has been a problem of difficulty in realizing a coin-type electric double-layered capacitor that is further miniaturized and capable of sufficiently ensuring fixing strength of a connection portion with a mounting board at the time of reflow-soldering the coin-type electric double-layered capacitor to the mounting board.
[Patent Document 1] Unexamined Japanese Patent Publication No. 2007-208137